Raining ants

Northern wood ants, Formica aquilonia, have a habit of dropping or "raining" off the branches of trees in their droves. Paul Haemig from Umeå University in Sweden has found that they do it most when there are birds around. When no birds are in sight, up to 12 per cent of ants can join a downpour, he says. But when birds come foraging, almost 30 per cent take the plunge ( AnimalBehaviour, vol 54, p 89).

Haemig says some ants are being swept out of the trees by air currents from the birds' wings, but he also claims to have seen ants deliberately jumping: he saw an ant "run faster for a few centimetres, and then jump off the tree by springing outward".

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